Now this is tricky. First of all it depends on what you consider cheap. For the answer let’s focus on wines that cost around 10 euro/dollar.
Whenever I have to pick a “cheap” wine I always try to go for the best possible price quality. Obviously it depends on where you live and what is available. Living in the Netherlands you can find lots of excellent wines that aren’t too expensive.
My strategy is to look at wine regions where you know the wines are good and the costs just aren’t too high. I wouldn’t buy a Bordeaux that costs less than 10 euro but for example some regions in Spain make affordable wines that can be a great go to. Think of a Godello wine from Rias Baixas, I know some great examples that cost less than 10 euros. Also a good Cava doesn’t have to cost more than 10 euro. In Italy you find good Pinot Grigio’s for under 10 euro. In France the wines from the pays d’Oc are great and affordable.
Another tip is to go to a wine store instead of the super market. Specialized wine stores tend to put lots of effort in the wines they select and will have some great finds under 10 euros in their assortment.